The present invention relates to a device for the extraction of gaseous samples and for thermal measurement above the burden of a shaft furnace, particularly a blast furnace.
It is known that one of the essential conditions for the optimum operation of a shaft furnace is that the gases should traverse the furnace in a faultless manner and that the ascending currents of gas should be uniformly distributed over the entire cross section of the furnace. After each charging operation, however, disturbances take place in the gaseous currents and may prevent the gases from traversing the furnace evenly. In order to remedy this drawback and to decide on the measures required, such as a change in the distributing of the charge, the composition of the gases and the temperature prevailing above the burden must be constantly monitored in order to detect any irregularity or sudden change in the operation of the furnace.
The known devices for the extraction of samples of gas and for thermal measurements above the burden of a shaft furnace comprise one or more probes, positioned radially above the burden and provided with gas sample extraction orifices. These known probes are either fixed, in which case the material of the burden is liable to fall on them while the furnace is being charged, or radially movable into and out of the furnace, in which case they have to be mounted in a special manner, causing a certain amount of obstruction, around the periphery of the furnace, in order to support them on the outside thereof.
The fixed probes and the radially movable probes no longer satisfy the requirements of modern blast furnaces having charging installations without bells (cones), such as that proposed, for example, in Luxembourg Pat. No. 59,207. These charging installations comprise a rotary spout which serves to discharge the material and of which the angle in relation to the vertical axis is adjustable, so that they enable the material to be distributed above the burden in the manner desired. To enable optimum use to be made of this spout and to take advantage of all the possibilities which it offers, the probe or probes positioned above the burden should be capable of providing measuring results for all points on the surface of the burden, so that the spout, which itself is capable of serving any point on the surface, can be controlled in accordance with these readings. The known probes give very little indication of the composition and the temperature over the entire cross section of the furnace and therefore do not provide a means for the detection of a local irregularity. The reason is that the probes are positioned radially without being capable of performing any angular movement about the vertical axis of the furnace. The measuring readings thus simply represent the gas composition and the temperature along one of more radii, according to the number of probes, above the burden.